This proposal is for years 21-25 of the Harvard AITRP, which proposes strong HIV/AIDS research training for applicants from 6 developing countries: Botswana, China, Nigeria, Senegal, Tanzania, and Thailand. The training is linked to specific sites and collaborators in these countries where active research collaborations are well established. Most of the faculty are associated with the Harvard School of Public Health (HSPH), which has extensive experience training students from developing countries. The research training is multidisciplinary, and linked to problems of prevention and treatment, including design of clinical trials, surveillance, mother-to-child transmission and chemoprophylaxis, vaccine design, drug efficacy and toxicity, drug resistance, behavioral issues, and HIV/AIDS health policy and cost effectiveness. The educational focus is on pre- and postdoctoral training in AIDS research, as well as shorter-term training in both Boston and the foreign sites. In the latter case, selected earlier AITRP trainees will be involved in south-to-south training in the developing country sites. The large number of foreign health professionals who have trained at HSPH serve, along with developing country collaborators, as a network for applicant referrals. The faculty advisors for the program have expertise in epidemiology (9), infectious diseases (7), immunology or virology (7), behavioral sciences (5), biostatistics (3), ethics (1), and international policy and economics (3). Most faculty members listed have active collaborations in one or more of the developing countries cited as partner countries, and have mentored trainees in the past. Numerous AIDS related courses, seminars, and workshops are available for trainees. Each trainee will have a principal advisor and a faculty advisory committee. Selection of trainees under a selection committee is based on previous academic performance, references, experience, and assurance that the candidates will return to participate in AIDS research in a developing country. The quality of the program will be monitored by a Training Advisory Group composed of experts from the US and from developing countries.